1. Field of the Invention
The present invention relates to a press-forming system manufacturing glass into a product such as an optical lens. More particularly, the present invention relates to a machine supplying raw materials and collecting formed products produced in the press-forming system having a plurality of press units, and also relates to a method of using the machine.
2. Description of the Related Art
An optical element made of glass such as an optical lens is usually manufactured by grinding and polishing and sometimes manufactured by press-forming. In a press-forming system, a glass material (called a preform) is set between a pair of dies, heated up to a glass transition temperature or more, and pressed by the pair of dies. It follows that patterns of the dies are transferred to the preform, thereby obtaining a formed product.
Since a relatively long process (including setting of a preform, heating, press-forming, cooling, and die opening, collecting a formed product) is required for forming glass into a product by a conventional press-forming system for glass, a plurality of press units is often arranged in parallel to improve the productivity. In such a conventional system, a transfer machine is usually arranged in each press unit to supply a preform to a press unit and collect a formed product from the press unit. However, not only the cost of equipment but also the footprint of the entire system is increased by providing a transfer machine in each press unit.
The present invention has been attained in view of the aforementioned problems associated with conventional press-forming system for glass. An object of the present invention is to enable to use a common transfer machine for transferring performs to and for transferring products from a press-forming system having a plurality of press units.
According to the present invention, there is provided a press-forming system for glass comprising:
a plurality of press units
a tray storing preforms to be supplied to the press units and products formed by the press units; and
a single transfer robot transferring preforms from the tray to each of the press units and transferring formed products from each of the press units to the tray, one by one.
According to the press-forming system for glass, since a common transfer machine is used for transferring preforms to a plurality of press units and transferring formed products from the press units one by one, the manufacturing cost and the footprint of the entire system can be minimized.
The inner space of the tray is preferably partitioned into a plurality of sections corresponding to the press units in number. Each section houses a plurality of pockets each being used for storing a preform or a formed product.
According to the present invention, the inner space of the tray is partitioned into a plurality of sections, which are assigned respectively to the press units. Therefore, in the case where the types of product to be formed in the press units differ from each other, it is easy to store preforms and products in different sections corresponding to the press units.
In addition, it is easy to inspect the different types of products as they were placed on the tray. Furthermore, a possibility that preforms and formed products are mistakenly placed in the same tray can be reduced.
In the press-forming system for glass, the trays are preferably replaced in accordance with the following procedure. A new tray is prepared by sequentially loading a requisite number of preforms in pockets of each section except the initial pocket to initially be used. Thereafter, when all preforms stored in any one of sections of the tray presently in use are used up, the tray is replaced with the new tray.
This feature is advantageous in the following point. When a formed product is obtained for the first time after the old tray is replaced with the new tray, the formed product is taken out from a press unit and loaded in the initial pocket of the section corresponding to the press unit, and then, another preform is picked up from the second pocket of the same section and successfully set at the corresponding press unit. Thereafter, when a formed product is obtained in another press unit, the formed product is picked up and loaded in a vacant pocket in the section of the tray corresponding to the press unit.
By virtue of this feature, even if an accident occurs in any one of the press units, preventing formed products from reaching a predetermined number per press unit, it is possible to minimize its effect upon the productivity of other press unit.